Machine readable bar codes have proliferated into all areas of business. They are produced with any number of technologies on the market today such as laser electrophotography, ink jet, thermal transfer printers, and conventional methods of printing such as mechanical numbering heads and lithographic printing. Among these is the Moore MIDAX technology which uses electron beam (or ion deposition) imaging techniques. Bar codes are commonly scanned by different methods such as the light wand, page scanners, hand held scanning beam pistols, and the familiar scanning beam machine scanners which are found in drug stores and supermarkets.
The vast majority of bar codes are printed as black bars on a white or lightly colored substrate, or in contrasting color bands as found on many consumer packages sporting the UPC bar codes in stores. Scanners of these bar codes work in the visible area of the electromagnetic spectrum or in the infra-red region. A common scanner at the check out area is the familiar red glow of the Helium-Neon laser scanner with a visible wavelength of 632 nM. Other scanners shoot out light in the invisible infra-red area of the spectrum between 800 and 950 nM.
Bar codes today are usually one dimensional, such as those found in the UPC label, code 3 of 9, interleaved code 2 of 5, or code 128. Two dimensional bar codes have also appeared on the market in the form of Cauzin Soft Strips and the UPS two-dimensional bar codes. The quest of using a two-dimensional bar codes, and high density single bar codes is to attempt to pack the maximum amount of information into the minimum amount of space on the package or other printed substrate.
According to the present invention a substrate, a method of coding a substrate, and a scanner utilizable with such a substrate, are provided which do maximize the amount of information in the minimum amount of space on a substrate, being more efficient or effective than two-dimensional bar codes or high density single bar codes. Typically, multiple layers of bar codes or other machine readable codes substantially increase the density of information gathered by the scanner heads within the same scan pass length or area coverage.
The invention also has another aspect. According to the invention it is possible to provide a security feature in which the bar code is not visible to the human eye but yet can be read by a scanner tuned to the correct wavelength range of electromagnetic energy (e.g. substantially the infra-red region of light). This security feature is in contra-distinction to proposals in the prior art, such as in U.S. Pat. No. 5,109,153, in which a photo-sensitive material is applied over a bar code and then--by selective exposure of the photo-sensitive material to high intensity light--the bar code is rendered unreadable, or modified, so that it is no longer read by a scanner as having the same data. Utilizing the security device of the invention a seemingly "invisible" bar code may still readily be scanned by an appropriate scanner.
According to one aspect of the present invention a substrate (such as paper, plastic, film, packaging material, or the like) capable of receiving and retaining imaging thereon is provided. The substrate comprises: A first machine readable identification code imaged on a predetermined area of the substrate, the first code opaque to a first predetermined wavelength range of electromagnetic energy and transparent to a second predetermined wavelength range of electromagnetic energy different from the first range. And, an overlay imaged over and at least partially covering the first code, the overlay transparent to the first predetermined wavelength range of electromagnetic energy and opaque to the second predetermined wavelength range of electromagnetic energy, different from the first range.
Typically the second range is substantially the visible spectrum of light and the first range is substantially the infra-red region of light, although much narrower spectral bandwidths can be utilized within a given region of the electromagnetic spectrum, or other regions of the electromagnetic spectrum (e.g., ultra-violet) can also be utilized.
For security environments, the overlay may comprise a security block which substantially completely covers the first code. The security block is typically applied by litho or flexographic techniques, or imaging applied by ink jet, electrophotographic or electrographic methods, or by electron beam or ion deposition techniques. The first code as well is normally imaged by ink jet, electrophotography, electrography, or be electron beam or ion deposition techniques.
Alternatively, in order to pack the maximum amount of information into the minimum amount of space, the overlay may comprise a second machine readable code, the first machine readable code in this case being transparent to the second predetermined wavelength range of electromagnetic energy. Third or more machine readable codes can also be imaged over and cover the first and second codes, the third code, for example, transparent to the first and second wavelength ranges and opaque to a third wavelength range, to which the first and second codes are transparent. The machine readable codes are preferably bar codes, and the first, second, third and subsequent codes typically comprise toner imaged on the substrate with electron beam or ion deposition techniques, electrophotographic or electrographic methods, or with ink jet.
According to another aspect of the present invention a method of coating a substrate comprises the following steps: (a) Imaging a first machine readable identification code on a predetermined area of the substrate, the first code opaque to a first predetermined wavelength range of electromagnetic energy and transparent to a second predetermined wavelength range of electromagnetic energy different from the first range. And, (b) applying an overlay over and at least partially covering the first code, the overlay transparent to the first predetermined wavelength range of electromagnetic energy and opaque to the second predetermined wavelength range of electromagnetic energy, different from the first range.
Steps (a) and (b) may be practiced so that the second range is substantially the visible spectrum of light and the first range is substantially the infra-red region. Step (b) may be practiced to apply a security block as the overlay, substantially completely covering the first code, by printing using litho or flexo techniques (or by imaging by electron beam or ion deposition techniques, ink jet, electrophotographic or electrographic methods).
Alternatively step (b) may be practiced by imaging a second machine readable code, in which case step (a) is further practiced by imaging the first machine readable code so that it is transparent to the second range. There may be the further step (c) of imaging at least a third machine readable code over and at least partially covering the first and second codes.
There also may typically be the further step of reading the machine readable codes. The reading step may be accomplished using first and second different scanner heads which emit light in the first and second wavelength ranges, respectively, in two different passes. Alternatively the reading step may be accomplished by mounting the first and second different scanner heads together so that both the first and second codes are scanned in a single pass (either by moving the scanner with respect to the substrate, or the substrate with respect to the scanner, or both).
According to yet another aspect of the present invention a scanner for reading machine readable codes, including by emitting light, is provided. The scanner comprises: At least first and second different scanner heads, the first scanner head for emitting light in a first predetermined wavelength range of electromagnetic energy and the second scanner head for emitting light in a second predetermined wavelength range of electromagnetic energy different from the first range. And, means for mounting the scanner heads immediately adjacent each other so that by single pass relative movement between a substrate and the scanner heads two different wavelength range machine readable codes on the substrate may be read at the same time.
The mounting means may comprise a portable housing, and the scanner heads may comprise scanner wands. Alternatively the mounting means may be a structure for mounting the scanners together in a stationary manner, such as in a supermarket check out counter. The second predetermined wavelength range is typically substantially the visible light spectrum, while the first range is substantially the infra-red region.
It is the primary object of the present invention to provide an efficient substrate, method, and scanner that allow the maximum amount of information to be packed in a given area on a substrate, and/or to provide a security feature. This and other objects of the invention will become clear from an inspection of the detailed description of the invention, and from the appended claims.